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Home › Pontiac › 2009 › G3 Automatic › Repair and Diagnosis › Engine Performance › System › Engine Controls And Fuel - 1.6L (LXV) › Diagnostic Information and Procedures › DTC P0128 › Circuit/System Testing

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the ECT sensor.
  2. Ignition OFF, test for less than 5 ohms between the low reference circuit terminal A and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, verify the scan tool ECT sensor parameter is at -40°C (-40°F).
    • If greater than the specified range, test the signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  4. Ignition ON, clear the DTC information with a scan tool.
    5. IMPORTANT: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.
  5. Install a 1A fused jumper wire between the signal circuit terminal B and ground. Verify the scan tool ECT sensor parameter is greater than 128°C (262°F).
    • If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, test or replace the ECT sensor.
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